As a clarification, PIA TS 135 is not proposed. It is a final PIA document. It has been submitted to the FAA for consideration as the next testing reference standard for TSO C23. So the TSO change is proposed, not the PIA document. Wether the FAA adopts it or not, the PIA document exists.

SAE is no longer interested in supporting this TSO with a standard, although theirs is still the current standard. That's why PIA has written one.

I doubt it as the last that I knew the FAA lost it and it has not been resubmitted yet. Since it has to be resubmitted it is being gone over again to make corrections that were found after it was sent the first time.